Corrosion-resistant laminate which consists of a metal of a single mass number deposited on a substrate

ABSTRACT

A highly corrosive-resistant metal having a high purity and a specific plane index is manufactured by ion beam deposition (IBD). A thin film having less defects and impurities is obtained. A magnetoresistant effect film for a magnetoresistant effect type magnetic head which is highly corrosion-resistant and exhibits excellent characteristics can be formed. In IBD according to the present invention, metal ions are provided with adjusted ion energy of 10 to 100 eV, and a metal having a particular mass number is selected by a mass separation electromagnet.

BACKGROUND OF THE INVENTION FIELD OF THE INVENTION

The present invention relates in general to an improved metallicmaterial which exhibits high corrosion resistance and, in particular, toa method of and an apparatus of manufacturing such a metallic materialwhich are effective to improve corrosion resistance of magneticmaterials and to improve reliability of structural materials, as well asuse of such a metallic material.

Examples of conventional processes of forming a thin metallic filminclude plating (electrolytic plating) which utilizes electric fieldeffect or chemical reaction in a solution, an evaporation process inwhich a film is formed under a vacuum by heating a metal serving as anevaporation source, and sputtering in which a film is formed from ametallic target by means of bombardment by gaseous particles. However,the electrolytic plating process which employs a solution suffers fromtechnical disadvantages in that impurity ions in the aqueous solutionenter the formed film and in that the formed film is physicallyunstable. The evaporation process is disadvantageous, because it isdifficult to form a high purity metallic film due to entering ofimpurity gas molecules during evaporation. The ion beam depositionprocess (IBD process) is free from any of the above-mentioned problems,and thus allows the formation of a uniform thin film which contains lessimpurities.

The floating zone melting process is known as a process for improvingthe purity of metal.

The IBD process is disclosed in, for example, JP-A-60-231924 andJP-A-61-87871. The former patent discloses a magnetic iron film formingmethod in which iron having a purity of 99.9% is evaporated as anevaporation source, and at the same time ionized together with nitrogengas and oxygen gas, and iron ions are irradiated onto a substrate toform a magnetic iron film. The latter patent proposes a method ofdepositing an organic metal or an alloy of organic metals on the surfaceof a substrate by irradiating an organic metal compound or a metalevaporation compound with an electron beam or an ion beam.

The ion source device employed in, for example, an ion beam apparatus ofprocessing a method surface, an ion implanting apparatus used inmanufacturing semiconductor devices, an ion beam deposition apparatus oran accelerator is constructed such that a substance containing the sameelements as desired metal ions is placed in a crucible provided with aheater, and a metal evaporation containing a desired metal ion isgenerated by heating the crucible. The generated metal evaporation issent to a discharge chamber to generate a discharge plasma containingmetal ions, like the Freeman type ion source. It is described in FIG.6.25 on page 203 of "Electron/Ion Beam Handbook (No. 2)" edited by the132nd Committee of Japan Society for the Promotion of Science andpublished by Nikkan Kogyo Shinbunsha in 1986.

However, in IBD, the process of generating a metal ion beam to form athin film has not yet been developed. Generation of a thin film of puremetal in the IBD process requires selection of a suitable metal compoundused to generate metal ion and the provision of a plasma chamber havinga configuration suited to extract the metal ion and to forward it to asubstrate.

In addition, the film forming conditions must be set in order to form afilm which is sufficiently corrosion-resistant to allow the film to beput into practical use.

Studies have been made about an increase in the corrosion-resistance ofa thick metal film, e.g., a thick iron film, formed by the floating zonemelting process by increasing the purity of iron. However, an increasein the corrosion-resistance of a thin film, such as a magnetic headfilm, has not been researched yet. Thus, the method of forming acorrosion-resistant thin metallic film has not been proposed yet, and itis thus difficult to form a corrosion-resistant thin metallic film whichis the fundamental structural element of a magnetic film.

Furthermore, in conventional technology, a crucible which is highlyheat-resistant and chemically stable at high temperatures is required inorder to stably generate desired metal ions over a long time, and thetemperature of the crucible must be controlled with a high degree ofaccuracy in order to maintain the pressure of the metal steam at a fixedvalue. Consequently, the ion source device has a complicated structure,making reduction in the size thereof difficult. It is also difficult toform a highly corrosion-resistant film.

SUMMARY OF THE INVENTION

One objective of the present invention resides in providing a metal oran alloy which is highly corrosion-resistant, a method and an apparatusfor manufacturing the same, and a magnetic disk device which is providedwith a magnetic head capable of reading data at a high sensitivity.

To achieve the above-described objective, the present invention providesa highly corrosion-resistant metal essentially having a single massnumber and having a purity of 99.99% or above.

The present invention further provides a highly corrosion-resistantmetal having a purity of 99.99% or above and a crystal grain size notgreater than 50 nm.

The present invention still further provides a highlycorrosion-resistant member in which a thin metallic film is formed onthe surface of a substrate. The thin film comprises a metal of a singlemass number or an alloy of a combination of a plurality of metals eachmetal having a single mass number.

The present invention still further provides a highlycorrosion-resistant member in which a thin metallic film is formed onthe surface of a substrate. The thin film is deposited with the closestpacked surface thereof perpendicular to the depositing direction, andhas a crystal grain size of not greater than 5 μm.

The present invention still further provides a method of manufacturing ahighly corrosion-resistant metal which comprises the steps of ionizing ametal, separating a metal ion of a single mass number, and depositingthe separated metal of the single mass number having adjusted ion energyin such a manner that no sputtering occurs.

The present invention still further provides a method of manufacturing ahigh corrosion-resistant metal which comprises the steps of ionizing ametal, separating a metal ion of a single mass number, and depositingthe separated metal of the single mass number having adjusted ion energyof 1 to 200 eV.

The present invention still further provides a method of manufacturing ahigh corrosion-resistant metal which comprises the steps of ionizing aplurality of metals, separating metal ions each having a single massnumber from metal ions, and alternately depositing the plurality ofmetals each of which has the single mass number having adjusted ionenergy in such a manner that essentially no sputtering occurs.

The present invention still further provides a method of manufacturing ahigh corrosion-resistant member in which a thin metallic film is formedon the surface of a substrate which comprises the steps of separating ametal ion of a single mass number, and depositing the separated metal ofthe single mass number having adjusted ion energy on the surface of thesubstrate in such a manner that essentially no sputtering occurs.

The present invention still further provides a method of manufacturing ahigh corrosion-resistant member in which a thin metallic film is formedon the surface of a substrate, which comprises the step of depositing ametal having adjusted ion energy in such a manner that essentially nosputtering occurs.

The present invention provides an apparatus for manufacturing a metalwhich comprises a metal ion implanting chamber for depositing a metal ona substrate, a discharge chamber for forming metal ions, an ionacceleration power source for accelerating the metal ions, an ion beamtransport pipe for introducing the accelerated metal ions into the metalion implanting chamber, a drawing power source for accelerating andintroducing the metal ions into the pipe at a high speed, a massseparation electromagnet for mass separating the metal ions introducedat a high speed, and a drawing voltage control lens for decelerating themass separated metal ions.

The electromagnet has a means for switching a current.

The metal ion implanting chamber is provided with a substrate holdingmeans for holding the substrate having a heater for heating thesubstrate.

The present invention provides a magnetic disk device with a magnetoresistant effect type magnetic head provided thereon. The magnetic headhas a structure in which a magnetic shield film, a lower gap film adomain control film, a magneto resistant effect film for converting amagnetic signal into an electrical signal utilizing a magneto resistanteffect, a shunt film, a soft film and a pair of electrodes for supplyinga signal detection current to the magneto resistant effect film areformed sequentially on a ceramic substrate. At least one of these filmsis made of either a metal having a single mass number or an alloy or acompound composed of a plurality of elements each of which has a singlemass number.

The present invention further provides a magnetic disk device with amagnetoresistant effect type magnetic head provided thereon. Themagnetic head has a magnetoresistant effect film for converting amagnetic signal into an electrical signal using a magneto resistanteffect, a pair of electrodes for supplying a signal detection current tothe magnetoresistant effect film, and a domain control layer forcontrolling a domain of the magnetoresistant effect film. Themagnetoresistant effect film is made of a metal having a single massnumber or an alloy composed of a plurality of metals each of which has asingle mass number.

The present invention still further provides a magnetic disk device witha magnetoresistant effect type magnetic head provided thereon. Themagnetic head has a magnetoresistant effect film for changing adirection of magnetization by sensing an external magnetization, a pairof electrodes for supplying a current to the magnetoresistant effectfilm, and a domain control layer for controlling a domain of the magnetoresistant effect film. The magnetoresistant effect film is made of ametal or an alloy which is composed of fine crystal grains having agranular structure and whose deposited surface has a desired singleplane index.

The present invention still further provides a magnetic disk device witha recording reproduction separation type thin-film magnetic headprovided thereon. The magnetic head includes, as fundamental components,a reproduction head portion and a recording head portion. Thereproduction head portion has a magnetoresistant effect film forconverting a magnetic signal into an electrical signal using amagnetoresistant effect, a pair of electrodes for supplying a signaldetection current to the magnetoresistant effect film and a domaincontrol layer for controlling a domain of the magnetoresistant effectfilm. The recording head portion has a first magnetic pole, a secondmagnetic pole whose one end is in contact with the first magnetic poleand whose the other end is not in contact with the first magnetic poleto form a gap, and a coil wound between on the first and second magneticpoles to convert a current which flows in the coil into a magnetization.The magnetoresistive effect film has a thickness ranging from 5 to 100nm and is made of a metal or an alloy having a fine granular structure.

The present invention is achieved by reducing an extracting voltage formetal ions obtained by ionizing metal atoms to a value which ensuresthat no sputtering or implantation occurs and by limiting a gas moleculedensity around a substrate on which a film is to be formed.

The ion energy must be 200 eV or below, preferably, between 10 and 200eV, when the temperature of the substrate is near ambient temperature.The gas molecules in the film forming chamber are composed of nitrogen,oxygen, carbon dioxide and water molecules. The important factor formanufacturing a highly corrosion-resistant metal is to reduce thepartial pressures of these substances, i.e., to reduce the gas densityof the film forming chamber to 10⁻⁴ Pa or below, preferably, to 10⁻⁷ Paor below by an evacuation devices.

The present inventors found that an alloy could be manufactured by IBDby heating the substrate when or after metal isotope ions are irradiatedthereto. The present inventors studied the relation between thetemperature and the ion energy when an alloy film was formed, and foundthat in the case of iron and nickel whose alloy ratio was 1:4, a film ofPermalloy was formed at 200° C. and at 20 to 100 eV. When thetemperature of the substrate is between 200° and 300° C., Permalloy ofFe and Ni is formed by alternately depositing Fe and Ni in layers eachlayer having a thickness corresponding to several atoms.

The present inventors examined the corrosion suppressing mechanism ofthe thin metallic film manufactured by the above-described thin metallicfilm manufacturing means, and found that the crystal structure of thesurface of the thin metallic film took only a single crystal-orientationplane and that the metal surface was composed of fine crystal clusterseach crystal having a size of 1 micron or below and thus had lessdefects. The present inventors consider that the regularly structuredsurface prevents entry of the molecules or ions of those substances andthus suppresses the reaction of anion, including oxygen, water orhalogen, with the metal which progresses corrosion.

In a practical example of the present invention, a thin iron film isformed on a conductive substrate. The surface of the thin iron film isessentially made up of (110) planes. To form this thin iron film, ironis ionized, and the iron ions are irradiated onto the conductivesubstrate at an acceleration voltage of 10 volts to 200 volts to depositiron atoms. Alternatively, a single type of iron isotope is selectivelyionized from iron atoms having iron isotopes, and the iron ion of thesingle mass number is irradiated onto the conductive substrate at anacceleration voltage from 10 volts to 200 volts to deposit iron atoms.The iron ion is irradiated in an atmosphere in which the density of thegas molecules and floating atoms other than iron atoms around asubstrate on which iron atoms are deposited is 3×10¹² pieces/cm³ orbelow to deposit iron atoms. The temperature of the substrate on whichiron ions are irradiated and thereby deposited is 300° C. or below,particularly, 200° C. or below.

At a high deposition energy, both granular structure and columnarstructure exist in a mixed state. In a body-centered cubic lattice, asthe ratio of (110)/((110)+(211)) reduces, the amount of corrosionincreases. A desired ratio of (110) plane is 0.5 or above. In eitherlattice, the most desirable ratio of the closest packed surface is "1".However, corrosion resistance is improved when the ratio is 0.5 orabove.

Furthermore, after the iron atom isotope is ionized, the iron iondeposition voltage is reduced to a value where neither sputtering norimplantation occurs, and the gas molecule density around the substrateon which a film is to be deposited is limited.

When the temperature of the substrate is near ambient temperature, adesired ion drawing energy is 200 V or below, with more preferable rangebetween 10 and 100 V. The gas molecules in the film forming chamber arecomposed of nitrogen, oxygen, carbon dioxide or water molecules. Theimportant factor for manufacturing a highly corrosion-resistant metal isto reduce the partial pressures of these substances, i.e., to reduce thegas density in the film forming chamber by an evacuation device.

Furthermore, in the manufacturing apparatus according to the presentinvention, iron ions of a particular mass number are directed toward thesubstrate by a magnet.

The present inventors examined the corrosion suppressing mechanism ofthe thin iron film manufactured by the above-described thin iron filmmanufacturing means, and found that the crystal structure of the surfaceof the thin iron film took the body-centered cubic lattice made up of(110) planes and that the iron surface was composed of fine crystalclusters each crystal having a size of 1 micron or below (particularly,from 0.01 to 0.5 μm) and thus had less defects. The present inventorsconsider that the regularly structured surface prevents entry of themolecules or ions of those substances and thus suppresses the reactionof anion, including oxygen, water or halogen, with the metal whichprogresses corrosion.

Iron compounds, such as Fe₂ O₃, Fe₃ O₄, FeCl₃ or Fe(OH)₃, are desirableas the iron ion source, and CCl₄ gas is preferable as the carrier gas.Deposition of a thin film is preferably performed under a super highvacuum of 10⁻⁴ Pa or above.

Although metals, alloys and inorganic compounds, such as oxides, nitrideor carbide, can be deposited by the IBD method according to the presentinvention, deposition of elements having the mass number whose contentis the largest among the elements which exist in the nature isdesirable. The mass numbers of the major elements whose content is thelargest are Mg24, Al27, Si28, Ti48, V51, Cr52, Mn55, Fe56, Ni58, Cu63,Zr90, Nb93, Mo98, Ru102, Ag107, Hf180, Ta181 and W184.

Applications of the IBD method according to the present inventioninclude formation of a magnetoresistant effect film for amagnetoresistant effect type magnetic head. Particularly, a Fe--Ni typealloy (Permalloy) is formed as the magnetoresistive effect film by theIBD method according to the present invention. Alternatively, a thiniron film, having a high purity, mass number of 58 and plane index of(110), is formed to a thickness of 10 nm or below by the IBD process ofthe present invention on a Permalloy film formed by conventionalsputtering, evaporation or electrolytic plating.

Other applications of the IBD process of the present invention includethe formation of lower and upper magnetic films for a thin-film magnetichead for writing, the formation of a coil, and formation of a TiNbarrier layer for interconnections having a barrier layer of a contacthole on a Si substrate for VLSI devices.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an ion beam deposition apparatus according to thepresent invention;

FIG. 2 illustrates an ion source;

FIG. 3 is a graph showing relationships between current density in NaCland the potential;

FIG. 4 is a graph showing relationships between current density in H₂SO₄ and the potential;

FIG. 5 is a graph showing relationships between the concentration ofimpurities and the degree of vacuum obtained during film formation;

FIG. 6 is a graph showing the amount of corrosion and the degree ofvacuum obtained during film formation;

FIG. 7 is a graph showing the amount of corrosion and the amount ofimpurities on the iron surface;

FIG. 8 is a graph showing the amount of corrosion and the planeproportion;

FIG. 9 is a graph showing the amount of corrosion and the work functionof iron;

FIG. 10 illustrates a magnetic disk device according to the presentinvention;

FIG. 11 is a cross-sectional view of a magnetoresistive effect typemagnetic head;

FIG. 12 is an enlarged view of the essential parts of FIG. 11;

FIG. 13 is a perspective view showing the overall structure of themagnetic disk device;

FIG. 14 is a perspective view of a slider on which the magnetic head isformed;

FIG. 15 is a perspective view of the slider and a load arm; and

FIG. 16 is a perspective view, partially in cross-section, of arecording reproduction separation head.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS EXAMPLE 1

FIG. 1 is a schematic view of an ion beam deposition device forgenerating a metal ion beam. FIG. 2 is a block diagram of a microwaveion source device for generating iron ions by a microwave dischargehaving a frequency of 2.45 GHz.

In the bottom surface of a discharge chamber 4 made of boron nitride andhaving dimensions of 20 mm×30 mm×50 mm, a recessed portion 21 having adiameter of 20 mm and a depth of 1 mm is provided. 500 mg of iron oxide(Fe₂ O₃) 3 having an average grain size of 10 μm is placed in thisrecessed portion 21. A lid 4 made of a conductive material is mounted onone side of the discharge chamber 4. An ion drawing slit 5 whose openinghas a size of 2 mm×50 mm is formed in the lid 4. A magnetic field havingan intensity of 900 Gaus is applied to the discharge chamber 4 region bymeans of a magnetic field coil 6, and carbon tetrachloride (CCl₄) isintroduced into the discharge chamber 4 from a gas introduction port 7at a rate of 0.5 cc per minute.

A high-density carbon tetrachloride (CCl₄) discharge plasma 9 isgenerated in the discharge chamber 4 by introducing microwaves of 300 Wfrom a magnetron 22 for generating microwaves of 2.45 GHz to thedischarge chamber 4 through a wave guide 21. An ion beam 1 is extractedout from the carbon tetrachloride (CCl₄) discharge plasma 9 generated inthe discharge chamber 4 by respectively applying +30 kV to theelectrically conductive slit 5 by means of an ion acceleration powersource 5 and -3 kV to a first ion extracting electrode 11 by means of apower source 12 and by grounding a second ion beam extracting electrode13.

The ions generated by a microwave ion source 20 shown in FIG. 2 weredeposited using an ion implanting device, shown in FIG. 1, with the ionsource 20 provided therein. The ion implanting device shown in FIG. 1includes the microwave ion source 20 shown in FIG. 2, the wave guide 21,the magnetron 22, a magnetron power source (not shown), the first iondrawing electrode 11, the extracting power source 12, the second ionextracting electrode 13, an ion beam transporting vacuum pipe 23, a massseparating electromagnet 28 for deflecting the ion beam by 90 degrees,evacuation pumps 10, an ion implanting chamber 25, a substrate 2, aheater 26 for generating the substrate 2, a substrate holding means 29,a substrate load lock chamber 24 for exchanging the substrates 2, a lenssystem 27, insulators 30, a reflection type high energy electron beamdiffraction device 31, an electron gun 32, a valve 33, a collectorelectrode for measuring an ion current, and an ammeter for measuring anion current.

The ion beam 1 drawn out from the carbon tetrachloride (CCl₄) dischargeplasma 9 at an acceleration voltage of 30 kV by operating the microwaveion source under the conditions shown in FIG. 1 was mass separated byscanning the magnetic field intensity of the 90- deflection massseparating electromagnet 28, and the ion current which flows in the ioncurrent measuring collector electrode was measured. It was found thatthe obtained ion beam was ⁵⁶ Fe⁺ ion beam. ⁵⁶ Fe⁺ ions are generated bythe heating of the ion oxide (Fe₂ O₃) powder 3 placed in the dischargechamber 4 of the ion source with the high-density carbon tetrachloride(CCl₄) discharge plasma 9 generated from the CCl₄ gas introduced throughthe gas introduction port 7 and by the plasma chemical reaction of theheated ion oxide (Fe₂ O₃) powder 3 with the CCl₄ gas plasma.

In this embodiment, Fe₂ O₃ powder was used to generate iron ions.However, ion oxides, such as Fe₃ O₄ or FeO₂, carbides, such as FeC,halides, such as FeCl₂, FeCl₃, FeCl₂.H₂ O, hydroxides, such as Fe(OH)₃,metal nitrides, such as FEN₄, organic metal compounds, such asFe(OCH₃)₃, metal alloy substances, such as Fe--Zr or FeS₃, may also beemployed to generate iron ions.

First, an ion beam 18 having a current amount of 5 mA was generated bygenerating Fe₂ O₃ +CCl₄ gas discharge in the ion source 20 and then bydrawing out the ion beam using a extracting power source 16 at a voltageVext=20 kV. The generated ion beam was mass separated using the massseparating electromagnet 28 for deflecting the ion beam at an angle of90 degrees and at a radius of 50 cm to take out Fe ions having a massnumber of 56. The potential of the ion source 20 was varied by anacceleration power source 17. The mass separating electromagnet 28 wasof saddle type which was divided into three portions along the peripheryof the vacuum pipe 23.

The mass separated iron ions were passed through the deceleration lens27 to decelerate the energy of the ions to the same energy as theacceleration potential in the ion source 20. The decelerated iron ionswere introduced into the film forming chamber 25 which was maintained toa degree of vacuum of 2×10⁻⁶ Pa from a flange 29 having a diameter of400 mm and mounted at the bottom of the film forming chamber 25.

In the film forming chamber 25, the Si (100) substrate 2 having adiameter of 2 inches was introduced onto the substrate holding mechanism29 provided with a heating function from the substrate load lock chamber24 in such a manner that the surface thereof on which a thin film was tobe formed was directed downward and that the surface lay in a horizontaldirection, as shown in FIG. 1.

A halogen lamp heater 26 which opposed the rear surface of the substratemounted on the substrate holding mechanism having the heating function26 was energized to maintain the temperature of the silicon substrate to300° C.

The mass separated Fe ions were irradiated on the silicon substrate 2having a diameter of 2 inches and disposed in a horizontal directionfrom a direction perpendicular thereto for 60 minutes. Consequently, athin film of pure ions which epitaxially grew in the crystal orientationof (110) could be obtained. The diameter of the film was 20 mm, and thethickness thereof was 500 nm.

In this embodiment, the iron ion energy was between 50 and 500 eV.However, a higher energy can also be used as long as it allows forformation of a thin film by the ion beam deposition process. A lower ionenergy assures the formation of a thin film having a fine and smoothsurface.

Table 1 lists the iron thin film forming conditions and the corrosionrate calculated from the polarization characteristics obtained bymeasuring the potential of the ion thin film immersed in a salt waterfrom the cathode to the anode thereof. It is apparent from Table 1 thatthe corrosion current density, which indicates the corrosion rate,obtained under the conditions of the present invention is one tenth ofthat obtained under the other conditions or below. The grain size of thefilms was not greater than 0.2 μm.

Particularly, it was made clear that when the ion energy in the ion beamdeposition process was 200 eV or below, a highly corrosion-resistantfilm could be formed. When deposition was performed with an energy ofnot less than 1 eV, particularly, not less than 10 eV, which was higherthan the ion energy in the evaporation deposition, a highlycorrosion-resistant thin film could be obtained.

When the crystal orientation of the surface of each of the iron filmswas examined with an X-ray diffraction device, it was found that inExample Nos. 7 through 10 of the present invention, shown in Table 1,the (110) plane, which was the close packed surface of a iron, wasselectively oriented and was directed in a direction substantiallyperpendicular to the surface, i.e., that Example Nos. 7 through 10 had apolycrystal structure which was similar to (110) single crystal.

When a distribution of the elements other than iron on the surface ofeach of the iron films was measured with a glow discharge massspectrometer, it was found that the amount of elements other than ironin Example Nos. 4 through 10 in Table 1 was one hundredth of that of theelements other than iron in Comparative Example Nos. 1 through 3. Thus,the present invention has the effect of reducing the amount ofimpurities.

FIG. 3 shows the polarization curves of the iron thin films manufacturedaccording to the present invention and of the iron having a purity of99.5% which is available on the market. The polarization characteristicswere measured by immersing the iron thin films and iron in 0.001M saltwater of 25° C. Whereas the corrosion current density of the 99.5% ironwhich is available on the market is 2×10⁻² A/m², the corrosion currentdensity of Sample No. 8 manufactured by the ion beam process accordingto the present invention with deposition energy of 100 volts was aboutone tenth of that of the iron which is available on the market, and thecorrosion current density of Sample No. 10 manufactured with depositionof 50 volts was about one hundredth of that of the iron which isavailable on the market. The thin films according to the presentinvention were made of iron having a purity of no less than 99.999% andmass number of 56.

                                      TABLE 1    __________________________________________________________________________                Degree of                      Substrate                             Ion accelera-                                     Corrosion current                vacuum                      temperature                             tion voltage                                     density             No.                (Pa)  (°C.)                             (V)     (A/m.sup.2)    __________________________________________________________________________    Conventional             1  10.sup.-2                      120    (Sputtering)                                     2 × 10.sup.-2    method   2  10.sup.-3                      200    (Evaporation)                                     3 × 10.sup.-3             3  --    80     (Plating)                                     5 × 10.sup.-3    Invention         High             4  10.sup.-5                      25     250     1 × 10.sup.-3    method         energy             5  10.sup.-5                      25     400     3 × 10.sup.-3             6  10.sup.-5                      25     500     5 × 10.sup.-3         Low 7  10.sup.-4                      25      50     3 × 10.sup.-5         energy             8  10.sup.-5                      25     100     1 × 10.sup.-4             9  10.sup.-5                      100     50     4 × 10.sup.-5             10 10.sup.-5                      25      50     1 × 10.sup.-5    __________________________________________________________________________

FIG. 4 also shows the polarization curves measured on the samples whichwere immersed in an 0.001M H₂ SO₄ aqueous solution of 25° C. Fe (99.5%)and Fe (99.99%) indicate irons which are available on the market.RRRH6000 and RRRH8000 correspond to the 99.999% iron and 99.99999% ironobtained by floating zone melting, respectively. It is clear from thefigure that corrosion resistance is improved by increasing the ironpurity. It is also clear that corrosion resistance is further improvedby increasing the iron purity and by forming a surface having aparticular plane index, like Sample Nos. 8 and 10.

FIG. 5 is a graphic representation showing the relation between thedegree of vacuum achieved during film formation and the concentration ofimpurities. FIG. 6 shows the relation between the degree of vacuumachieved during film formation and the amount of corrosion measured insalt water. FIG. 7 shows the relation between the concentration ofimpurities and the amount of corrosion. As shown in FIG. 5, an increasein the degree of vacuum markedly reduces the concentration ofimpurities, such as oxygen or other metal elements. Particularly, theconcentration of impurities is about 1.5×10⁻³ pieces when the degree ofvacuum is 10⁻⁵ Pa. As shown in FIG. 6, when the degree of vacuum is 10⁻⁵Pa, the amount of corrosion is 10² μg/cm². The amount of impurities whenthe amount of corrosion is 10² μg/cm² is about 10¹⁵ pieces/cm², as shownin FIG. 7. Particularly, when the amount of impurities is 3×10¹²pieces/cm² or below, the amount of corrosion rapidly reduces. Thus, adesired degree of vacuum is 10⁻⁷ Pa or above.

FIG. 8 shows the relation between the proportion of (110) plane in apure ion and the amount of corrosion in 25° C. salt water of 0.001mol/liter. The ratio of (110) plane to (211) plane was adjusted bychanging the ion acceleration voltage, i.e., the ion energy, in the IBDapparatus according to the first embodiment from 30 eV to 500 eV. As theion acceleration voltage increases, the proportion of (211) planeincreases. Although the selected iron isotope is 56, it has beencertified that an increase in the ion acceleration voltage increases theproportion of the crystal orientation other than the close packedsurface in other metals, as in the case of ion isotope 56.

FIG. 9 shows the relation between the measured value of the workfunction of various irons and the amount of corrosion in 25° C. saltwater saturated with air. The work function of the surface of the ironfilm formed by IBD is 4.65 eV, which is higher than a normal value, 4.5eV. The threshold value of electron emission from such a surface hascorrelation with strengthening of the oxide surface film which indicatesan improvement of corrosion resistance.

EXAMPLE 2

Thin films of various elements were formed using the ion beam depositiondevice shown in the first embodiment.

After the metal ions were drawn out from the ion source 20 by means ofthe acceleration voltage power source 17, they were directed toward thesubstrate 2 by the magnet 28. Thereafter, the metal ions were condensedonto the substrate which had the same potential as the groundedpotential by the lens 27 to deposit a metal on a predetermined area andthereby form a thin metal film. Iron, nickel, manganese, aluminum,copper, tungsten, tantalum, niobium were used to form films. Oxides ofsuch metals were used as the metal compounds which were the materials ofplasma for ionizing the metals. The film forming temperature was a roomtemperature, and the used ion energy was 50 eV. Table 2 shows theproportion of the amount of corrosion measured on the metal films afterthey were immersed in salt water of 1 mol/liter for 1 hour to the amountof corrosion of the high purity metal which is available on the market.The thin film of any metal formed according to the present inventionexhibited high corrosion resistance.

The mass numbers of the metals of the deposited thin films were Fe56,Ni58, Mn55, Al27, Cu63, W184, Ta181, and Nb93, respectively. The samedeposition can be performed using the other mass numbers.

                  TABLE 2    ______________________________________    Type of thin   Proportion of the amount of corro-    metallic film formed by                   sion in salt water to that of the    IBD (name of element)                   same metal marketed which is 1    ______________________________________    Fe             0.001    Ni             0.02    Mn             0.005    Al             0.07    Cu             0.2    W              0.3    Ta             0.01    Nb             0.1    ______________________________________

EXAMPLE 3

Fe and Mo ions were formed using oxides of these metals in the ionsource, and Fe56 ions and Mo36 ions were irradiated concurrently to forma highly corrosion-resistant thin Fe--C--Mo low alloy film at a roomtemperature.

The mass separated ions were supplied upwardly from the bottom of thefilm forming chamber 25 with an ion energy of 1000 eV for thirty minutesto irradiate the iron substrate 31 having a diameter of 50 mm anddisposed horizontally in the film forming chamber 25 evacuated to 2×10⁻³Pa. Fe and Mo were alternately deposited from the evaporation source 3by switching the current of the electromagnet 28. These metals werealloyed when the formed layer was as thick as a single atom and when thesubstrate was preheated to about 300° C.

Consequently, a highly corrosion-resistant thin Fe--C--Mo low alloy film22 could be formed to a thickness of 2 μm on the iron substrate 2 at asubstrate temperature which was a room temperature. The corrosion rateof the formed thin film 22 in a saturated salt water was 0.02 mm/year,which was two orders in magnitude smaller than the corrosion rate of anormal thin iron alloy film of 2 mm/year. The thin film was attached tothe substrate 2 firmly.

EXAMPLE 4

FIG. 10 is a schematic view of a magnetic disk device 4000 according tothe present invention. As shown in the figure, the magnetic disk device4000 includes a plurality of magnetic disks 112 which are piled on topof one another along a single axis (a spindle) at equal intervals, amotor 111 for driving the spindle, a magnetic head group 123 held on amovable carriage 114, a voice coil motor 115 for driving the carriage114, and a base for supporting these components. The magnetic diskdevice 4000 further includes a voice coil motor control circuit forcontrolling the voice coil motor 115 according to the signals sent froman upper apparatus, such as a magnetic disk control apparatus, and aread-write circuit having the function of converting the data sent fromthe upper apparatus into a current which is to be supplied to themagnetic head according to the write system and the function ofamplifying the data sent from the magnetic disk 113 and of convertingthe amplified data into a digital signal. This read/write circuit isconnected to the upper apparatus through an interface.

The reading operation of the magnetic disk device 4000 will now bedescribed in detail. The upper apparatus gives an instruction on thedata to be read out to the voice coil motor control circuit. The voicecoil motor 115 drives the carriage 114 by the control current from thevoice coil motor control circuit to move the magnetic head group 113 tothe position of the track on which the designated data is stored at ahigh speed and accurately locate the magnetic head group 113 at thatposition. To perform this positioning of the magnetic heads 113,positioning magnetic heads 113a connected to the voice coil motorcontrol circuit detect the position on the magnetic disks 112. Further,the motor 111 supported on the base rotates the plurality of magneticdisks 112 mounted on the spindle. Next, the designated magnetic head isselected according to the signal from the write/read circuit. After thestarting position of the designated area is detected, the data signal onthe magnetic disk is read out. To perform this reading, the magnetichead 113 connected to the write/read circuit exchanges data with themagnetic disk 112. The read out data is converted into a predeterminedsignal. The converted signal is sent to the upper apparatus.

The track density of the magnetic disk according to the presentinvention is from 2600 to 20000 tracks per inch. The linear recordingdensity thereof is from 65 to 200 kiro-bits per inch. The area recordingdensity determined by the product of the track density and the linearrecording density is from 170 to 4000 mega bits per square inch.

The magnetic head mounted on the magnetic disk device according to thepresent invention may be a recording reproduction separation type head3000 shown in FIG. 16. The recording reproduction separation typemagnetic head 3000 is made up of an electromagnetic induction type thinfilm read magnetic head 2000 and a magnetoresistive read magnetic head(hereinafter referred to as an MR head) 1000.

In the MR head 1000, the reproduction output per track is 5 to 10 timesthat of a conventional electromagnetic induction type thin filmread/write magnetic head when the amount of floating and the type ofmagnetic disk medium in the reproduction operation are the same.Furthermore, the reproduction output of the MR head 1000 is not affectedby the peripheral speed of the magnetic disk.

Therefore, even when the track width of the MR head is reduced, i.e.,even when the track density of the magnetic disk medium is increased, ahigh reproduction output can be obtained. Further, even when the linearrecording density of the magnetic disk medium is increased, a highreproduction output can be obtained.

In the present invention, since the Barkhausen noise which is readilygenerated in an electrical signal from the magnetic disk duringreproduction is restricted and since the base line variations of thereproduced waveform generated due to that noise can be restricted to 3%or below at any disk rotational speed, any sensing current and anyamount of floating, a noiseless electrical signal can be obtained, and ahigh S/N ratio can be assured. These allow for the reproduction of dataat a high sensitivity.

Furthermore, it is possible according to the present invention to obtaina stable, high output and noiseless electrical signal within theoperation temperature range.

Furthermore, since the recording head and reproduction head are providedseparately in the present invention, a magnetic core 130 of therecording head 2000 can be made of a material having a high saturatedmagnetic flux density Bs. As a result, the writing magnetic field can beintensified and made sharp, and recording at a high linear recordingdensity is thus enabled. Further, even when the track width is narrowed,a high writing magnetic field can be maintained, making recording at ahigh track density possible. These enable the coercive force of themagnetic disk medium to be increased.

Therefore, in a magnetic disk device which incorporates the MR head 1000according to the present invention, high output and noiselessreproduction are achieved regardless of the size of the disk.

Therefore, high density recording is enabled regardless of the size ofthe magnetic disk. Even when the disk diameter is reduced to from 1.5inches to 6.5 inches, recording and reproduction can be performed at amagnetic disk rotational speed of 3500 to 5000 rpm, at a track densityof 2.6 to 20.0 ktpi and a linear recording density of 60 to 200 ktpi inthe magnetic disk device according to the present invention, and an arearecording density of 170 to 400 mega bits per square inch can thus beachieved.

Furthermore, even when the bit density and track density are increasedin order to satisfy the capacity required for a small magnetic diskdevice and the disk diameter is reduced to 1.5 to 3.0 inches, readingand writing can be performed sufficiently. Therefore, the disk size canbe reduced to the above-mentioned value, and a small magnetic diskdevice having a large capacity can be provided.

A magnetic disk device which assures an increase in the recordingdensity and data storage capacity but permits reduction in the datatransfer speed is useless. The higher the linear recording density, thehigher the data transfer speed. In this invention, a linear recordingdensity from 60 to 200 k bits per inch can be obtained, and a hightransfer speed can thus be obtained.

Furthermore, since the magnetic core 130 of the recording head 2000 canbe made of a material having a high Bs in the present invention, asufficiently high writing magnetic field can be maintained even when thenumber of turns of a conductive coil 110 is reduced. As a result, thenumber of turns can be reduced (FIG. 16), thus reducing the inductanceof the recording head 2000 and making the data writing operation at ahigh frequency possible.

The reproduction output of the MR head is not affected by the peripheralspeed, and the data reading operation at a high frequency can beperformed.

The electrical signal obtained using the MR head 1000 according to thepresent invention is noiseless. Therefore, it is not necessary for theobtained electrical signal to be passed through a special circuit forprocessing the Barkhausen noise in order to convert it into a digitalsignal.

Thus, it is possible according to the present invention to obtain a datatransfer speed from 6 to 9 mega bytes/sec.

When the data transfer speed increases, the data access time (the timerequired for positioning) must be reduced. In the present invention, adesired data access time is from 5 to 10 milli-seconds.

A desired disk rotational speed is 3500 rpm or above, and a desiredaverage rotation waiting time of the magnetic head is 6 m second orbelow in terms of the data transfer speed. Here, the rotation waitingtime is the time during which the magnetic head, which has moved to apredetermined track position, is kept waiting for the magnetic disk tobe rotated in order to write data to a predetermined position on thattrack or to read out data from a predetermined position.

In the present invention, since the diameter of the magnetic disk can bereduced, a high-speed seek can be achieved. Further, since theBarkhausen noise of the MR head 1000 can be restricted, the access timecan be reduced.

If Barkhausen noise (base line variations) is generated during thesignal reading operation from the magnetic disk by the MR head, the MRhead must read out the data signal from the magnetic disk again. At thattime, the reading operation is performed in the above-mentioned cycleagain. In, for example, a magnetic disk device which incorporates an MRhead for generating Barkhausen noise at a possibility of 50%, the accesstime is delayed by 1/30 second. In the magnetic disk device according tothe present invention, since Barkhausen noise of the MR head can berestricted, the access time can be reduced to 5 to 10 milli seconds.

FIG. 13 is a perspective view showing how the magnetic disk deviceaccording to the present invention is accommodated in a predeterminedspace.

A head/disk assembly unit (HDU) 73, which is made up of a head/diskassembly (HDA) 71 and an electronic circuit portion 72, is accommodatedin a vessel 700. In the vessel 700, the length of one side of the bottomthereof is between 0.3 and 1.5 m, and the height of the vessel 700varies from 0.2 to 2 m according to the capacity of the device. In FIG.13, A and B indicate passages of air through which clean air is suppliedto the circuit boards in the HDA and HDU.

FIG. 14 is a perspective view showing how the recording reproductionseparation type magnetic head according to the present invention isformed on a predetermined slider. Reference numeral 81 denotes a slidermade of, for example a non-magnetic ceramic. Reference numeral 3000denotes a recording reproduction separation type magnetic head having aconfiguration shown in FIG. 16. There are four current terminals for therecording reproduction separation type magnetic head because therecording head and the reproduction head are provided separately.Reference numeral 83 denotes a medium opposing surface which opposes themagnetic disk.

FIG. 15 is a perspective view showing how the slider shown in FIG. 14 isformed on a load arm.

Reference numeral 91 denotes a load arm for supporting the slider 81.Reference numeral 93 denotes a gimbal spring for maintaining thedistance between the slider and the magnetic disk to a fixed value. Thedistance between the magnetic disk and the recording reproductionseparation type magnetic head 3000 formed on the distal end of theslider 81 in a magnetic disk device activated state is generally calledan amount of floating, and is one of the important factors of theperformance of the magnetic disk device. In the magnetic disk deviceaccording to the present invention, this amount of floating can bereduced to 0.2 μm or below.

FIG. 16 shows the recording reproduction separation head 3000 mounted onthe magnetic disk device according to the present invention. The MR head1000 used only for reproduction is formed on a non-magnetic ceramicsubstrate 101, and the electromagnetic induction type recording head2000 used only for recording is formed above the MR head 1000. In FIG.16, the right half of the recording head 2000 and the right half of theMR head 2000, respective layers formed above a signal detectionelectrode 60, are omitted.

In FIG. 16, reference numeral 210 denotes a conductor coil. Referencenumeral 130 denotes upper and lower magnetic cores. An insulator film,designated by 220, is formed between the upper and lower magnetic coresto provide an electrical insulation.

In the recording reproduction separation type magnetic head 3000according to the present invention, since the recording head 2000 doesnot perform the reading operation, a high magnetic permeability and lowmagnetostrictive characteristics, which would be required for reading,are not required for the magnetic cores 130, and high Bs characteristicsalone, which would be required for writing, are required. Thus, thematerial having a high Bs can be used to form the upper and lowermagnetic cores 130, as mentioned above. Furthermore, since the writingcharacteristics are not substantially affected by the magnetostrictiveconstant of the magnetic cores 130, the selection range of the materialand the margin of the material composition can be expanded, facilitatingthe manufacture of the recording head 2000. Consequently, throughput andyield can be improved. Furthermore, an element used to improve corrosionresistance, such as Cr, can be added, and a recording head 2000exhibiting excellent corrosion resistance can thus be manufactured.

FIG. 11 is a perspective view showing a typical magnetoresistant effecttype magnetic head according to the present invention which is the mostsuitable embodiment to solve the above-described problems. FIG. 12 is anenlarged cross-sectional view as seen when looking from the direction ofthe surface which opposes a magnetic recording medium.

The magnetoresistant effect type head 1000 shown in FIG. 11 includes alower shield film 110 formed on a ceramic substrate 101 made of, forexample zirconia, a lower alumina gap film 120 formed on the lowershield film 110, an oxide antiferromagnetic film 45 of, for example, aFe--Mn alloy or NiO formed on the lower gap film 120, a separation film77 made of, for example, alumina and disposed on the oxideantiferromagnetic film 45 at least at a magnetic field sensing portionof a magnetoresistant effect film 40, the magnetoresistant effect film40 formed on the separation film 77 in such a manner that it covers apredetermined area of the oxide antiferromagnetic film 45 on which theseparation film 77 is not disposed, a shunt film 50 of, for example, Nband a soft film 55 of, for example, a Ni--Fe alloy which are formed onthe magnetoresistant effect film 40, a signal detection electrode 60 of,for example, Nb formed on the soft film 55, an upper gap film 70 formedon the above-described respective films, and an upper shield film 80formed on the upper gap film 70. The feature of the present inventionresides in the structure of a domain control layer for preventing noisecalled Barkhausen noise, the magnetoresistant effect film and theelectrode film.

The operation and material of the respective layers and films will bedescribed below.

The upper and lower shield films 80 and 110 have the function ofpreventing a magnetic field other than the signal affecting themagnetoresistant effect type film 40 and of increasing the signalresolution of the magnetoresistant effect type head 1000, and are madeof a soft magnetic alloy, such as an NiFe alloy, an NiCo alloy or a Cotype amorphous alloy. A preferred thickness thereof is between 0.5 and 3μm.

The upper and lower gap films 70 and 120 disposed adjacent to the upperand lower magnetic shield films 80 and 110 have the function ofelectrically and magnetically separating a magnetoresistant effectelement from the upper and lower shield films 80 and 110, and arepreferably made of a non-magnetic and insulating material, such assilicon oxide, glass or alumina. The thickness of the upper and lowergap films 70 and 120 affects the reproduction resolution of themagnetoresistant effect type head 1000, and thus depends on therecording density desired for the magnetic disk device. A preferablethickness is between 0.4 and 0.1 μm. A preferable distance between thepair of signal detection electrodes 60 is between 0.5 and 10 μm. In themagnetic head mounted on the magnetic disk device according to thepresent invention, the reproduction track width can be narrowed to, forexample, 0.5 to 2 μm. The portion of the magnetoresistant effect film 40located between the signal detection electrodes 60 is called a magneticfield sensing portion, and contributes to the reading of the signal froma magnetic disk. In order to apply a transverse bias to themagnetoresistant effect film 40 to convert the magnetic signal from themagnetic disk into a linear electrical signal, the shunt film 50 and thesoft film 55 are provided. The magnetoresistant effect film 40 is formedof a ferromagnetic substance whose electrical resistance changesaccording to the direction of magnetization, such as an NiFe alloycontaining 10 to 20 wt % of Ni, an NiCo alloy, an NiFeCo alloy or any ofthese alloys which contains no more than 3 wt % of Ru, by the iondeposition process according to the present invention. A desiredthickness thereof is between 0.001 μm and 0.045 μm. The depositedsurface thereof is (100) surface. The shunt film 50 and the soft film 55have fine crystal grains having a grain size of 5 nm or below. A desiredlength of the portion where the domain control film 45 is in directcontact with the magnetoresistant effect film 40 is not less than 3 μmin the longitudinal direction of the magnetoresistant effect film. Inthis way, no domain wall is generated in that portion, and the oxideantiferromagnetic film 45 can thus function as the domain control film.

In order to supply sufficient current, e.g., 1×10⁶ to 2×10⁷ A/cm², tothe magnetoresistant effect film 40, the signal detection electrodes 60are made of a material having a low electrical resistance, such as Cu,Au, Nb or Ta.

The shunt film 50 applies a transverse bias of a level sufficient toimprove the sensitivity of the film 40 to the magnetoresistant effectfilm 40. The direction of application of this bias field isperpendicular to the direction of application of a bias by the domaincontrol film. The method of applying a transverse bias using a shuntfilm is referred to as shunt biasing. In shunt biasing, a thin metalfilm, such as Ti, Nb, Ta, Mo or W, is formed, as the shunt film, on themagnetoresistant effect film 40. The thickness of the shunt film isbetween 0.01 and 0.04 μm. Furthermore, since the transverse bias fieldvaries according to the current which flows in the shunt film, both thethickness and a specific resistance of the shunt film 50 must beadjusted. A desired specific resistance is 1 to 4 times that of themagnetoresistant effect film 40.

The other method of applying, to the magnetoresistant effect film 40, atransverse bias of a level sufficient to improve the sensitivity of thefilm 40 and make the film suitable for use in a magnetoresistant effecttype head for high-density magnetic recording is soft-film biasing.

In soft-film biasing, a ferromagnetic film having soft magneticcharacteristics is formed adjacent to the magnetoresistant effect filmwith a non-magnetic layer therebetween in order to efficiently apply amagnetic field generated by the current which flows in themagnetoresistant effect film to the magnetoresistant effect film. Thesoft film 55 is made of NiFeRu, NiFeTa, NiFeRh, CoZrCr or MnZn ferrite.

Although it is possible to employ either of these biasing methods, theuse of composite biasing achieved by forming the soft film 55 on theshunt film 50 (non-magnetic film), as shown in FIG. 11, is effective.The magnetoresistant effect type head 1000 according to the presentinvention has employed composite biasing.

The method of manufacturing the magnetoresistant effect type head 1000will now be described. In this method, thin film formation andpatterning are conducted using the sputtering, etching andphoto-lithographic processes.

First, an NiFe alloy is deposited to a thickness of 2 μm to form thelower shield film 110, and then alumina is disposed to a thickness of0.3 μm to form the lower gap film 120. Thereafter, the lower shield film110 and the lower gap film 120 are shaped in a predetermined form. Atthat time, the end portion of the lower shield film 110 is inclined withrespect to the substrate surface, as shown in FIG. 11, in order toprevent breakage of the signal detection electrodes 60 formed in such amanner that they cover the lower magnetic shield film 110 at the endportion of the lower shield film 110. Next, the oxide antiferromagneticfilm 45 is formed to a thickness of 0.04 to 0.2 μm on the lower gap film120, and then the separation film 77 is formed to a thickness of 0.01 to0.02 μm at a predetermined position. At that time, the separation film77 is formed by the lift-off method so that it can be disposed at theposition of the magnetic field sensing portion of the magnetoresistanteffect film 40. The two end portions of the separation film 77 may betapered in order to prevent stepping of the magnetoresistant effect film40. Further, the separation film 77 may also be formed by ion milling.Next, an NiFe alloy film is formed to a thickness of 400 Å on theseparation film 77 as the magnetoresistant effect film 40. Subsequently,an Nb film is formed to a thickness of 400 Å as the shunt film 40, andthen a CoZrNb film is formed to a thickness of 400 Å as the soft film55. Thereafter, the soft film 55, the shunt film 50, themagnetoresistant effect film 40 and the separation film 77 are shapedconcurrently such that they have forms shown in FIG. 1 by, for example,ion milling. After a double-layer film of gold and titanium is formed toa thickness of 0.1 μm as the signal detection electrodes 60 andprocessed, alumina is deposited to a thickness of 0.3 μm on thedouble-layer film as the upper gap film 70. Next, an NiFe alloy film isformed to a thickness of 2 μm as the magnetic shield film 80, and thenalumina is formed as a protective film, thereby completing manufacturingof the magnetoresistant effect type head 1000.

In the magnetoresistant effect type magnetic head according to thepresent invention, the sensitivity is improved without the magnitude ofmagnetic exchange coupling being reduced. The end portions of themagnetoresistant effect film can function as the domain control layerswithout the magnetoresistant effect film being cleaned, which can causevariations in the characteristics or noise. In the method ofmanufacturing a magnetoresistant effect type magnetic head according tothe present invention, variations in the performance of the plurality ofmagnetoresistant effect type magnetic heads, caused by variations in thecharacteristics of the domain control layers, can be suppressed. Inother words, in the magnetoresistant effect type magnetic head accordingto the present invention, the magnetoresistant effect film has thefunction of the domain control layer and at the same time has theportion where the direction of magnetization changes freely. These canbe achieved by shaping the separation film 77 in a desired form. Whenthe electrodes are formed within the area where the direction ofmagnetization changes freely, the portion between the electrodes can bemade the reproduction track width, thus preventing generation ofBarkhausen noise. Further, the track width can be narrowed only bynarrowing the portion between the electrodes. Furthermore, thesensitivity of the portion between the electrodes becomes substantiallyuniform, and the reproduction sensitivity is thus greatly improved.

In order to increase the portion of the detection current which flowsinto the magnetoresistant effect film, an oxide film is used as thedomain control layer 45. Examples of the oxide films having the domaincontrol effect include ferromagnetic films or antiferromagnetic films.However, antiferromagnetic nickel oxide (NiO) is preferable from theviewpoints of stability to an external magnetic field, the blockingtemperature and the ease of manufacture. In addition to NiO, hematite(which may be substituted for α-Fe₂ O₃) or NiO which contains a magneticelement, such as Fe, Co or Ni, or a rare earth type magnetic element,such as La, Ce, Pr, Nd, Pm, Sm, Gd, Tb, Dy, Ho, Er, Tm or Yb, can alsobe employed as the material of the oxide antiferromagnetic film 45.

Suitable examples of the material of the separation film 77 include Al,Ti, Cu, Nb, Mo, Ta, W, Ti, V, Cr, Rh, Ru, Zr, Pd, Ag, Pt, In, Sn, Re,Os, Ir, Au, alumina (Al₂ O₃), silicon oxide (SiO₂), titania (TiO₂),hafnia (HfO₂), zirconia (ZrO₂) and carbon (C). The separation film 77may also be a non-magnetic alloy film composed of a combination of atleast two of the above-described metal elements. It may also be made ofa material composed of an oxide, carbon and a third element. Al₂ O₃,SiO₂, TiO₂, HfO₂ and ZrO₂ provide insulation. Therefore, when theseparation film 77 is made of any of these substances, the currentdensity which flows in the magnetoresistant effect film 40 can beincreased, and the sensitivity of the magnetoresistant effect typemagnetic head can be improved.

The thickness of the separation film 77 is between 10 and 300--As shownin FIG. 11, the magnetoresistant effect film 40 is formed on theseparation film 77. Since the magnetoresistant effect film 40 is formedin such a manner that it covers the separation film 77, if the thicknessof the separation film 77 is large, the magnetoresistant effect film 40may be stepped. Therefore, a thin separation film is desired, and adesirable thickness is 200 Å or below. The critical film thickness ofthe separation film formed as a continuous film by, for example,sputtering is not less than 50 Å. Therefore, the preferable thickness ofthe separation film 77 is between 50 and 200 Å. In order to effectivelyapply a bias from the end portion, it is preferred that the thickness ofthe magnetoresistant effect film 40 be larger than that of theseparation film.

Although the MR head provided with the shield films has been described,the present invention can also be applied to a non-shieldmagnetoresistant effect type magnetic head, a yoke magnetoresistanteffect type magnetic head, a magnetoresistant effect type magnetic headfor magnetic tapes or a magnetic sensor which utilizes themagnetoresistant effect of a ferromagnetic film.

In this embodiment, the shield films 110 and 80 which constitute themagnetoresistant effect type thin-film magnetic head media opposingsurfaces are made of an iron nickel alloy. The antiferromagnetic film 45is made of an iron manganium alloy. The magnetoresistant effect film 40is made of an iron nickel Permalloy which contains 1 wt % of Ru. Theseparation film 77 is made of an oxide film of Al. The shunt film 50 ismade of Nb. The soft film 55 is made of an Ni--Fe alloy which contains 1wt % of Ru. The electrodes 60 are made of Nb. The respective films areformed by IBD. The respective films are patterned using photoresists.The thickness of each of the films is converted from the ion beamcurrent. Each of the thin metallic films is formed to a desiredthickness ranging from 10 to 3000 nm. In IBD, after the metal elementhas been positively ionized, metal ions are taken into the vacuum vesselby accelerating them with a negative electric field. After the isotopeions having the same mass number are selected by the mass separationmagnet, the ion energy is decelerated to 200 eV or below to deposit themetal ions having the same mass number.

The film formation by IBD in this embodiment was conducted using theapparatus shown in FIG. 1. Oxides of various elements were used as theion sources. The degree of vacuum was 10⁻⁵ Pa. The acceleration voltageof the ion source was 50 volts. The temperature of the substrate was300° C. The mass numbers of the elements are the same as those shown inthe second embodiment. A thin alloy film was formed by alternatelydepositing metals in layers each of which had a thickness correspondingto several atoms by switching the electromagnet 28 according to theelements to be deposited at a predetermined current value. Preferably, asingle layer had a thickness corresponding to a single atom (a singlelayer is deposited within 10 seconds). Each of the films was a thin filmhaving a very small grain size of 5 nm or below, particularly, about 1nm. The closest packed surface, (110), for a body-centered cubic latticeand, (100), for a face centered cubic lattice, was formed on thedeposited surface. Thus, highly corrosion-resistant films were formed.

Particularly, whereas the film formed by conventional sputtering has athickness of about 1 μm, the magnetoresistant effect film 40 of thisembodiment has a thickness of 0.02 μm while having the magneticallyequivalent characteristics to those of the conventional film. Therefore,a high performance reading can be achieved.

Electrodes for a magnetic head were formed using W in place of Nb by IBDin the same manner as the above-described example. After oxide WO₃ wasionized by a carbon tetrachloride steam plasma, W184 was selectivelydeposited on the soft film 55 at a position of the electrodes 60 shownin FIG. 11. Conventionally, W electrodes were corroded during thepolishing/washing process of the element surface. However, theelectrodes formed according to this method were highlycorrosion-resistant and highly reliable because the specific resistancethereof substantially did not increase after the polishing/washingprocess and was 15 μΩcm or below.

In another example, after the shield films 110 and 80, themagnetoresistive effect film 40 and the soft film 55 were formed bysputtering from Permalloy, iron 58 having a purity of 99.999% and (110)plane and grain size of 5 nm was deposited under the conditions ofExample No. 7 in the first embodiment. In this way, a magnetic headhaving a high corrosion-resistance and high sensitivity was obtained.

What is claimed is:
 1. A member resistant to electrochemical corrosionwhich comprises a metallic thin film formed on a surface of a substrate,said film consisting essentially of a metal of a single mass number oran alloy of a combination of different metals, each different metalhaving a single mass number.
 2. A member resistant to electrochemicalcorrosion which comprises a metallic thin film formed on a surface of asubstrate, said thin film being formed by ion beam deposition and havinga surface with a close packed crystal structure and having a crystalgrain size of not greater than 5 μm, said thin film consistingessentially of a metal of a single mass number or an alloy of acombination of different metals, each different metal having a singlemass number.
 3. A member resistant to electrochemical corrosionaccording to claim 2, wherein said thin film consists of a metal havinga single mass number, the content of which is largest among thoseisotopes of the metal which occur in nature.
 4. A member resistant toelectrochemical corrosion according to claim 3, wherein said metal of asingle mass number is an isotope selected from the group consisting ofSi28, Mg24, Al27, Ti48, V51, Cr52, Mn55, Fe56, Ni58, Cu63, Zr90, Nb93,Mo98, Ru102, Ag107, Hf180, Ta181 and W184.
 5. A thin film of pure ironhaving resistance to electrochemical corrosion, said thin film beingformed on an electroconductive substrate and having a surface crystalstructure oriented in the (110) plane, said thin film consistingessentially of a metal of a single mass number or an alloy of acombination of different metals, each different metal having a singlemass number.
 6. The thin film of claim 5, wherein said iron has a massnumber of Fe56 or Fe57.